System for telephone-trunking.



S. H. BROWNE.

SYSTEM FOR TELEPHONE TR'UNKING.

APPLICATION FILED APR.3.1905.

Patented May 4, 1909.

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SYSTEM FOR TELEPHONE TRUNKING.

APIfLIOATION mum APR.3.1905.

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S. H. BROWNE.

SYSTEM FOR TELEPHONE TRUNKING.

APPLICATION FILED APR. 3. 1905.

920,258. I Patented y 4, 1909.

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S. H. BROWNE.

SYSTEM FOR TELEPHONE TRUNKING.

APPLICATION FILED APR. 3. 1905. 920,258, Patented May 4, 1909.

5 SHEETS-SHEET 4.

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SYSTEM FOR TELEPHONE TRUNKING.

APPLICATION FILED APR. 3, 1905. 920,258. Patented May 4, 1909.

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SIPNEY IIAND BROWNE, OF PITISBURG, PENNSYLVANIA, ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

SYSTEM FOR TELEPHONE-TRUNKING.

Specification of Letters Patent.

Patented May i, 1909.

Application fi1ed April3, 1905. Serial No. 258,5M.

' nected by trunk circuits over which theconnections are completed. My object is to provide equipment by which the required acts on the part of'the operatonfirst receiving a call are reduced to a minimum in number and simplicity, and also by which the likelihood of error is much reduced as compared withpresent common practice;

' In present common practice, when a call isreceived from a patron in the execution of whose order it is necessary to connect with a linefite'rminating in, a central ofiice distant from that in which the call is received, one of ,two general'plans is followed; First, the op'-, erator taking the order may communicate with. a distant operator, in the distant central oflice, giving the number of the line with vhich connection is required,-a-nd the operator in the distant office will then select a trunk and connect it with the line required, giving to the first operator as reply to her order [the designating number of the trunk used, ,thatthe first operator may connect the callin patron v. ith that trunk; this involves the se ection of a trunk by the operator in the distant central oilice. Second, the operator answering'the call and taking the patron's order may test trunks reaching the distant central office and when an idle trunk is found may connect the calling patron with it and 45:1ingthe distant exchange; the operator in the distant central oflice then iii-response to thatring will answer the calling iatron and will connect him with the desired tcloplur-ur line this involvesthe'selection of a trunk l:- -t'hei operator first receiving the call.

My invention in its system and in the an paratus herein described, provides for the proper and expeditious prosecution of tho subscribefs order without any selection of truukagon thepartfof any operator, Such j trunk selection being taken out of the required manual operations and being made wholly automatic.

My invention provides that the operator first answering a call, learning that the call is for a substation telephone served by a line terminating in a distant central oilicc, may connect the calling line with an idle trunk of that grou without any ircliminary manual method of testing, and t ereby will transfer the call immediately to the central oliice in which the line desired by the calling atron terminates. In my description, I sha show equipment which provides that calls received at a'n'exchange are received directly upon plugs instead of being received upon jacks requiring the insertion of a plug before the operator can place herself in communication with the calling patron; which provides that the operator first answering a call, learning that the call is for a distant oilice, may take any vacant jack reaching that ollice and thereby transfer the call immediately to that cities; and which rovidcs further that the call thus s.v1tch e( forward \\'1l.l terminate e one central o'llicefin an exchange equipped according to 1ny; invcntion, Figs. 2 and 2" show another central office in the same e1 change also equipped according to my invention. In each ollicc is shoe n equipment for receiving a call from the distant (Till-1'0, in: Wellas for receiving a call from a patron and for forwarding it to the distant ollico; and Fig. 3 is a diagranunatic view, illustrating: more in detail a suitable 00111100llOil-i'ogisltting meter.

In Fig. l thorn is illustrated oquipmiui by which a (all originating at a :-iiilr-:tui oii tel-1- phono, as Sfmay in tormiimtod upon a con nocling plug. as 51, in the hand oft-1n operator advised of the ro uizoiue uai ol' the i atrou at the substation ichphouc and pr-o'i idrd with connecting: jacks, as .31 in Fig. i". adapted i0 r'rcoi'i'o the (Ollllirilllfl plug: 3%. to (:oinplclrf'or 'io forward the call originated by the patijou at substation telephone A telephone line is shown "at 1?, connecting tit. one end jwith a substation lclcpliouc, 8, and, at the other end with the central oilicc line Ill i io

equipmentshown below at the left of Fig. 1 I a plurality of radial contacts and provides and in part in Fig. l The central oilice line equipment consists of a call receiving equipment, comprising a group of multiple jacks, as 96, accessible to connecting plugs, as '76, Fig. 1 for the completion of calls originating on other lines and re uiring connecting *ith the line shown, am a call'forwarding equipment, for forwarding to a central 'ollrce operator a call originating at the connected substation telephone, 8. T he call forwarding equipment consists of an automatic switch designated as a Whole 20, and associated relays l0, I6, 19, 40, the interrupter ,7 and battery 9, said interrupter and battery being common to many lines. An clectromagnetically operated call register, or service meter, is indicated at 200, its magnet core and associated electric circuits being shown. In this register, the attraction of the armature shall add one to the number previously registered by the dials of the device, the return of the armature being accomplished without mechanical effect upon the counting train, as is common in simple electric counting dew 108$.

The. automatic switch may be of any desired or preferred type of electromagnetically controlled circuit selector. It is well known in the art of telephony, to construct a switch having a'plurality of contacts arranged to project inwardly from a cylindrical surface, said surface being either a complete section of a cylinder, or merely a segment of a cylinder, and to arrange, supported by an at the center of the-cylindrical surface, movable electrical terminals ada ted .to make contact successively with t 1e fixed points when the supporting aiiis is rotated a llllllll' example is the stronger automatic switch. In such a switch the essential elements consist of a cylindrical surface, elect cal contact points lixcd in said cylindrical surface, a rotatable shaft occupying the position of the axis of the cylinder, terminals attached to said shaft occupying the position of radii of the cylinder and adapted to connect with the tired contacts in the cylindrical surface, a ratchet Wheel attached to said shaft, a retractile spring attached to said shaft or ratchet wheel, holding the part against a stop or in its position of rest, a holding pawl engaging the teeth of actuation through an angular distance equiv' alent to the angular distance bctwcen con tact points in said cylindrical surface. In

such switches the usual practice provides for ratchet Wheel, means for withdrawing said position of rest.

for fixed contacts arranged in groups or sets, so arranged and located that the radial (ontacls inane connection respect lvcly uiih the individual fixed contacts of a given group when th shaft is art-a given position, and as the shaft moves, the radial terminals more from set to set of the fixed contacts and clfect elcctri a l connection with the respective contacts of each set as. progress is made from set to set.

111" Fig. 1, l have shmvn two sets of lined contact points connected with conductors 2], 22, 23, 24, 25, and conductors 131, 32, 33, 34, a set of radial terminals is shown at ll, 12, 13, i l, 15; the ratchet \TllCCl is shown at 5; the rctractilc spring is shown at 6; the holding pawl 2 is shown as the armature to the upper core of magnet 4 means for n ithdrawing said holding panl is shown in mag net 4; the driving panl 1 is shown pivotally attached to the armature of magnet 3, and means for actuating said driving par-. l is shown in magnet 3 and its associatu circuit and battery 9. It is common also in such switches to include an operating part holding an electric circuit open by the separation of a (pair of electrical contacts during the perio of time when the rotatable shaft remains in its position of rest, and to permit such contact pair to make connection when the shaft makes its first stcu away from its Such an electrical contact pair is called an oilL-nornial snitch and is shown at 46 in Fig. 1. i

The mechanism involved in the switch designated as a whole 20 in Fig. (or snitch 03 in Fig. 1 which is similar to snitch 20) therefore is one of a general type well known in the art and one which readily may he coin structed and used without further description hero. The circuits l;:' which the actuating means for the driving pawl l is controlled and hy'which the releasing means is controlled are disclosed in the paragraphs of this specificationfollouing. I The circuits shown in Fig. 1 are in accordance with the invention of my application, Serial No. 222,645, filed August 29th, 1904.

in Figs. 1 and 2 is shown a double-track trunk for forwarding telephone callsfrom one central oilico (such as shown in Figs. i 1") to another central ollice (such as shown in Figs. 2*, 2 the trunk being conl'mctml by circuit conductors 64, across the bottom of Fig. 2. The complete double-track trunk consists of the connecting circuit conductors (int, provided at each on'r'l with a call eceiving equipment consisting at one end (see Fig. l of a'plumlity 0 sets of uniting contacts, as si, 253, S5 and the relay 66, a switching and signaling equipment, as the plug 76, and associated elements shot 11 adjacent to that plug, and an interference equipment comprising the relays 6'? and 68.

The object of the interference equipments is to operate, when the trunk is taken at one of its call receiving equipments, to isolate the office, leaving the switching and signalingequipment operative in the said distant central oflice. he similar call-receiving equipment at the other end of the trunk consists (see Fig. 2*) of-scts of waiting contacts, as S1, 82, 83', S t, 85, relay 66, plug 76, and associated elements adjacent to the plug, and interference equipment comprising relays 67 and SSI r i To enable the operator in charge of the connecting plug 51, Fig. 1 to connect with the trunk 64, hcr switchboard position is provided with a plurality of trunk jacks, a558, each ot which has an automatic switch,

as 63, containing the above mentioned plurality of sets of waiting contact )oint', as 81,82, 83,84, 85, pertaining to a plurality of trunks, and a set of movable terminals, 71, 72, 73, 74, and )n.t1'olling parts or relays 5t), 60, 61,62, and resistance 99. Thus equipment is provided to enable the operator to insert the connecting plug 51 into any vacant jack 58, thereby causing the auto matic action of the switch 63 to select a trunk, connect the jack 58 with it, and to actuate the interference mechanisms 67, 65 and 67, 68 'to isolate from the trunk the waiting contact points 81, S2, 83, 84', 85 at the other end.

Equipment is provided in central office, 2*, 2 similar in all respects to that provided for central Oll lCG 1, it, so that all of the operations herein described as originating in central oilice 1, 1 may be equally Well accomplished when originating in central ollice 2,

switch 63 immediately connects said jack, and therefore the calling SllbStllbEl, with the first idle trunk, as 64, 65, leading to the sclected distant central ol'lice, and in so doing renders said selected trunk impossible of use by any other automatic switch at either of its ends and also lights a signal lamp, as 93 before a telephone ())(.Iilt0l' in the distant central ollicc; the telephone o mrator thus secondarily selected then takes the order of the calling atron directly from substation telephone 8 v means of ll( ll\'( V 102 and tclcphone set 55, and connects the trunk plug 76 with the linc of the tclcphonc, as i, called for, one of whose multiple jacks; as 96, noccssarily is located within rcach ol' the said trunk opcrator by reason of the primary sclcction exercised by the operator who first answered the call; the called station is rung by the second operator, by operation of her ringing key 103, and upon the answering ol' the called station, the service motor as 200, connected with the calling line, is opcratcd to record the successful connection. in disconnection, the calling line controls a signal before the first operator, and the lirst operator controls a signal before the second opcrator, before whom is also a signal controllcd by the called line.

In the application of my .invention as 1 shown in thc accompanyi'ng drawings, I have used automatic switches each adapted to seserves, becomes active.

2 the connection over the trunk being made in reverse order. To the parts and elements shown at the central otlice of Figs. 2 and 2*, I have applied the same reference numerals, with the addition of prime plied to corresponding central oflicc at Figs. 1 and 1 The progress of a callthroughout the system shown in the tour sheets of drawings is as follows: When the receiver at substation telephone Sis taken l'roni' the hook, the automatic switch 20 iminraliatclv sclccts the first idle trunk loading to a tclcphonc operator, and

thus lights a signal la mp, as 45.. associatcdwith a plug, as o I. hciorc such operator; said operator then litlillr; thc HIlHCX'llXlhi order, and

l'carningthat thc llnc required terminates in a distant cent ral ollicc, as that shown in Figs. 2* Z'hinuncdiatcly connccts the aid plug, with out any process of test, with any vacant jack designated'as belonging to that central o'tlice, as the jack "58. whereupon the automatic controlled by a driving pawl 1, am marks as area )awl 2, sald (lllVllW )a'wl bcm controlled I h h parts shown at the lect auton'ratically the lilst idlo trunk circuit, of a series of such circuits connected with the switch, whenever the onc controlling telephone line or trunk circuit, which theswitch ()no of these automatic switches appears in each of the tour sheets of drawings, and the parts and functions common to all of these switches (designated as a whole, 20 in Fig. 1*, 63 in Fig. 1 '20 in Fig. Q'Band 63 in Fig. 2") in the several drawings are. as follows, referring to Fig. 1: The switch consists of a fixed frame bearing magnets, pawls, springs, etc., and

rot

also sustaining a rotary part adapted to be a holding )y magi'lct 3 and both of said pawls being controlled by magnet 4 to rclcasc the. rotary part of the switch. The rotary part of the switch consists of a shaft 220 to which is attachcd the ratchct wheel 5, one end of the volutc spring 6, and the fivc wipers 11, 12, 13, 14, 15; these wipers are n'ioviug electrical contacts permanently connectedto the conductors pertaining to the one line or trunk which that :nitomatic switch serves, and adapted to liltLkC temporary electrical connection with circuit tcrminals pertaining to trunks with which it is dcsircd to connect the line or trunk served. The fixed portion of the switch supports a )iurality of sets of waiting contacts, of which one set is shown connected to' conductors 2]., 22,,23,24. 25.

19, winding of magnet 3 and interrupter 7 and another set is shown connected to conductors 31, 32, 325, 34, 35. The driving pawl 1 under influence of magnet 3, is adapted to move the rotary part of the switch, one step at a tnne; normally, the wipers are not in 'connection with any of the sets of waiting contacts, but upon the first energization' of magnet 3, the rotary pa t of the switch moves one step and the wipers-are brought into connection with the first set of waiting contacts, viz., those connected tofconductors 21, 22, 23, 24, 25; at the next energizetion of magnet 3, the second step of the rotary part of the switch brings the wipers into contact with the second set of waiting con tacts, viz., those connected with conductors 31, 32-, 33,34, 35, which are provided with a complete trunk equipment identical with that shown associated with conductors 21,

22, 23/24, 25, and so on for the entire conilemcnt of sets of waiting contacts, which in practice probably would be twenty-five to fifty sets, representing as many trunks. The progress of the rotary part, step by step,

is secured by the interrupter 7 in the circuit 5 of magnet 3, such interrupter being a continuously operating device, separate from the automatic switches. stopping of the rotary part is accomp ishcd by relays and circuits associated with the trunks and lines.

The operation of the circuits and electrical mechanism shown in Fig. 1 in res onse to a call initiated by subscriber at telep lone 8, is as follows :The removal of the receiver from the hook at substation telephone 8 permits f current to flow from battery 9 through relays 10 and 16, and line 17 to ground at 18, thus energizing relay 16 to open its contactand energizing relay 10 to close its contact, thus permitting current from battery 9 to flow through contact-of relay 10, contact of relay 19, wiper 14, waiting contact and conductor 24, armaturecontact 26, armature 27, winding 28 of relay 2,9 and to ground at battery 30 thereby energizing both relays 19 and 29. The energization of relay 19 attracts its armature, thereby interrupting the previously traced circuit through magnet 3 and stopping the switch with its wipers in engagement with contacts 21 22, 23%, 24, 25. Said energization of relay 29 permits current to flow from battery 30 through armature 36, armaturc contact 37, rcsistmice coil 199, conductor and waiting contact 23, wiper 13, conductors 38 and 39 through winding of relay 40 to ground, energizing relay 40 and causin it by thenetuation of its armature to open t 1e cir- The startin and cuit of the winding of relay. lOand to transfer the conductors of the line 17 to wipers 11 and 12, thus providing path for current from bat- 1 tery 30 through relay 41, elements 22, 12, 17, 8, 17, 11, 21 and relay 41 back to battery 30, energizing relay 41 and giving path for cur rent from one pole of battery through armature 42, winding 43 of relay 29, armature contact 44, armature 27 winding 28 and to other pole of battery 30, completing the 7 energization of relay 29 and. breaking the connection between armature and contact 2726-. 11' tl re first trunk encountered by the wipers had been alrmidy in use, the relay 29. of that trunk would have been energized, and 80 the armature rontact 27-26 would have been open, thus giving no path for current through relay 19, so that the path for current from battery 9 through. magnet 3,, continued through the armature of relay: 19, would. have been interrupted at the interrupter 7', releasing armature of magnet .3, again closed at inl terrupter 7, energizing magi r 3 the second i time, stepping the wipers forward into connectionwith the second set of waiting con- 1 tacts, where if relay 29 had been already can i ergized the process would have been repeatcd, and so on until a set of contacts was,

found in which the relay 29 was not energized, thus giving path for current through relay 19 and so effecting the connection of i the line 17 with that trunk and the stopping.

l of the automatic switch in that position untilconditions were proper for disconnection.

Electrical contact 45 and ielectrical contact spring 46 have a tendency to close together i when not restrained, but a projection 47 on ratchet 5 holds 46 away from 45 so long as the ratchet 5 is in its position oft, rest; however, at

the first step of tnc ratchetb, the projection 7 is moved to permit the contact pair 45f46 to close; upon the hanging up of the receiver at the substation telephone- 8, the circuit is broken and current ceases to flow through relay 16, thus permitting its farmature contact to close and to ive path fjor'current from battery 9 throng 1 armature contact of relay 16, magnet 4, contact pair 4546 back to battery 9, thus energizing magnet 4 until by return of the rotary part of the switch to normal the contact bctween45 and 46 is opened, thus releasing magnet 4. Thus it is seen that as soon as the receiver is removed from the hook at substation telephone 8, automatic switch 2O-hcco1ncs active, se-

lects the first idle trunk, connects the calling line with that trunk, and by the cricrgization of relay 41 gives current from one pole of battcry '30 through lamp 48, armatures 49 and 50 to the other pole of said battery, causing 1125 lamp 48, in the switchboard near plug 51, to

i glow signal to the attendant telephonc operator thata calling line has been conncctedto plug 51.

The operator-,whose equipment is shown at 54 in Fig. 1 may be termed a subscribers ,operator, because she serves calls originating for her office upon subscrlbers hnes, while the operator whose equipment is shown at 55 in Fig. 1*? may be called a trunk operator because "she serves calls originating for her oihce upon trunks incoming from the exchange ot lice shown in Figs. 2 -.'2 In similar tcrminolog the operator at 54 in Fig 2" is a-subscri ers operator and the op erator at 55 in Fig. 2 is a trunk operator.

, 7 4, 75, and a plurality of sets ofwaiting contacts, as 81, 82, 83, 84, 85.

' circuit 4 Between the offices of Figs. 1 and Figs. 22" are provided a plurality of trunk circuits, each consisting of two conductors, as 64 and 65. The trunk conductors 6465 have associated with them the plurality of waitingcontactstl, 82, 88, 84, 85 in multiple ina plurality of said switches as 63 before the subscribers operators of the office; each trunk has also a-relay as 66 and a pair of relays as 67, 68, whence the trunk is extended by condor gors 69, 70 to a plug 76 acting as a terminal of the trunk before an operator at 95. 'lrunlr conductors 64, are equipped at their distant end, in the office shown in Figs. 22 with similar apparatus.

The )urpose of the relay 66 is to open the between the conductor leading to conmet 84 and ground in manner similar to the action of relay 29 (Fig. 1*) and for the same purpose, viz., to place busy test conditions upon the waiting contacts connected with that conductor. The purpose of the relay 67 issimilar, via, to place busy test conditions upon the waiting contacts in the ol'lice of Figs. 1. 1 when the trunk has been taken for use from ofi'ice of Figs. 2"-2"; the purposoot' relay 68 is to remove the connection of extension conductors 69---70 from the trunk when the trunk has been taken for use from the ollicc of Figs. 1. -1". The two rclays, 67 and 68, are so related that by the operation of one the other is rendered inoperative. The object of the pair of relays, 67, 68 is to permit intercommunication over I the trunk, eitln-r from ollicc of Figs. 1 1 to ollice of Figs. 22 or in the reverse direction from oilicc of Figs. 2---2" to ollicc of Figs. 1--l",

rent, froin grounded battery 30, Fig. 1, flows, from the body of said plu through to ground, and current from the same source also flows from the ring of said plug 51 through winding of relay 59 and contact of relay 61 to ground; the energization of relay 60 gives path for current from battery 76 through contact of'relay 60, contact of relay 62, magnet'77 and interrupter 78 back to battery, thus operating the rotary part of the automatic switch 63; by the action 'of the winding of relay 60 and contact 0 relay 61 interrupter 78 the said rotary art progresses step by step until a trunk is ound in which neither relay 66 nor 67 is energized, at which time current will flow from grounded battery 76, wiper 75, contact 85, contact. of relay 67 and winding of relay 68 to ground, energizing relay 68 and disconnecting from the trunk .the extension 69, 70; also current from battery 76 will flow through winding of relay 62,

wiper 74, contact 84, contact 79, armature 80, winding 87 of relay 66 and contact of relay 67 to ground, energizing relay 62 which attracts its armature stolpping the action of the automatic switch.- telay 66 is also energized by this circuit and attracting it armature 80," closes contact 86 and gives path for current from grounded battery 76 through winding of relay 61, wiper 73, con-i tact 83, winding 88 of relay 66, contact 86,

armature 80, winding 87 of relay 66, and contact of relay 67 to ground; this energization of relay 66 also opens armature contact 79 -80. The energization of-relay 61, by the circuit above traced therethrough, opens the circuit of current through winding of relay 60, releasing the armature of that relay; the opening of contact 7 9-80 interrupts the circuit through winding of relay 62, releasing the armature of that relay; the energization of relay 61 connects conductor 89 to wiper 7] already in electrical connection with contact 81 and consequently with trunk conductor 64, and also connects conductor 90 with wiper 72 already in electric al connection with contact 82 and therefore with trunk conductor 65, and current previously flowing through relay 59 and the contacts of relay 6] to ground, now flows through relay 59, conductor 90, armature of relay 61 and its front contact, wiper 72, waiting contact 82, and trunk conductor 65 to the distant oflicc (see now Fig?) and over conductor 91 to armature of relay 68 where the current divides, one portion passing through the winding of relay 67 to ground and the other portion passing over extension conductor 70' and through winding of relay 92 to ground. The energization of relay 67 opens the circuit between conductor 84 and ground, thus giving busy test conditions to all automatic switches in central ofiipe of Figs. 2"2 the energization of relay 92 gives path for current from battery 95 through lamp 93 contill tarts of relay 94 and contacts of relay 92 to ground; lamp 93 is located in the switchboard near plug 76', and .by the glowing of lamp 923 the telephone operator using the equipment at 57 is notified that a calling line is connected with plug 76, and she therefore completes the connection by taking the patrons order by means of her telephone set and key 102 and selecting and connecting with the proper jack, in a'nianner similar to that of the operator using equipment at 54, who first received the call.

I have described the operation of portions of the apparatus in showing how a call is received from a subscriber, first in the central ollice of Figs. 1-2 and then from a trunk, in the central oftice of Figs. 2--.---2

closes circuit for lamp 97, but the armature of relay 100 simultaneously opens said lamp circuit, thus preventing the lamp from glowing; also armature 49 of relay 98 opens the circuit of signal lamp 48, extinguishing that lamp and leaving no signal before operator at 54, indicating that her work is temporarily completed.

The insertion of plug 51 into jack 58 causes automatic switch 63 to select its first idle trunk as 64, 65 to the central oiliee of Figs. 23", establishes for said trunk busy test conditions at all accessible points, and

by the energization of relay 92 causes the glowing of a signal lamp associated with a trunk plug located before a tele hone operai shall describe now the progress eta complete connection, originating at substation telephone 8 on a line terminating in central office of will be given ii detail which liavenot been so given before; 0

A ftillOlifli', substation telephone 8 desires to ca 1 substation telephone 8 and takes his receiver from the hook; immediately automatic switch 20 selects its first idle trunk, establishes busy test conditions upon the. muliial lamp associated with a trunk plug before a subscriber-s operator, as signal lamp 48 as tiolc 'ucks of the callin r line and li hts asi l .l i b n using equipment 55 tor in the distant ofiice, as signa lamp 93 associated with trunk lug 76 before operator The operator at 55 by means of key 102 communicates directly with the calling patron, takes his order for connection with substation 8, tests a multiple jack as 96 of the line serving substation S and finding that the line is not busy in-' sorts plug 76 in jack 96 and actuates the signal bell of substation telephone 8 by means of the ringing key 103'. I

The insertion of plug 76 into jack, 96 gives path for current from battery 95 throug i. relay 94 to the body conductor ,of jack 96 and thence over conductor 106 and throu h the \VllHllIi of rela 107 toround,'

a s LY g ener izing relays 94 and 107', thelatte'r oi" WliiCili isolates line 17 from the equipment associated with automatic switch 20. Be-

hiy 94, thus energized, opens the circuit of lamp 93 and extinguishes that signal, but also closes by contacts of another armature a circuit by whichcurrcnt flows from grounded sociated with trunk plug 51 before. operator using equipment54 operator at 5 1 by means of key 52 rouiinuiiicuics with the patron. takes his order for connection with Sllbhltl" battery 95 through the contacts of relay 94, lamp 108 and contact of relay109 to iound,

- thus illuminating lamp 108 as a signa to the lion h", recognizes l'rom thrdircctory numher that substation is to be reached by. of fire of Figs. 2 i2", and inserts" the trunk plug 7)! into any jack connecting with that i-i-ui rnl ollicc, as ja k 71H: ringing key 52; is not used in such a connection, nor is signal lump HT uscd, those (l-El'l"i.lll.\ being provided l'or use in such calls as would require connection with a called line also teriiiiniiting in ollice of l igs. I i there being no necessity n such rails to use a trunk to another oilice ol' the exchange. iy the illHtl'lI-lO li ol' plug 51 into jack 5%, pathis givcir lorcurrcui l'romgrounded battery 30 through relay J8 to body conductor of jack 58 whence it iiows to; ground throughrcsistinn-e99and iilsolhrough rel.-iy (it) aiid'coiitacts of relay (3] to ground.

lzilh is given also for current from grounded battery 1-H) through relay I00, conductors it)! and no, the latter containing the winding of f relay 5!), and through the contacts of relay r (it to ground. iin armature of relay 98 through contacts of relay (m operator at 55 that the receiver at substa lion tele )hoiie S has not been taken from the hook. liy means of key 103 the patron at substation telephone 8 is jfl'called, and as stated above, when he answers the call and removes his telephone from the hook he closes the circuit through his hook switch and gives path for current from battery Q5 ihrough re ny 109, condiuitorlli), lug 7,6"v jack no, line 17, substation telep lone S. line 1?, jack U6, plug'76, conductorill and relay 1 12 to ground, thus energizing rclays lot) and 112'. By energization of relay Hit), circuit through lamp 108 is-iiiterrupicd and that hunp is'extinguislied, leaving all signals before the operator at 57 dark, and iudirzii lllgliil'itl that the party rung has answered tln rnll, and that she-has no further immediate duties in connection with the call.

By theenergizatioii of relay" H2, path is given for current from battery 95 f-l contacts of relay 112 to conductor tit) i I 7 to conductor ill] , batteryf206 through meter winding 207 con-' ance 115, wiper 15, conductor 201 and wind- 200, ground at 203 is connected directly to the makingof'the contact with ground at 'Lac't point45, contact spring 46 and to planned. This"en ergizes core m and the atter attracts 117$ "armature 205, actuating operative position by a spring g ant stop and countin tralnK in their advanced posihook; this, howevex, cannot be taken as it its " 1.13 and relay 114 to ground at batterv 30'.

therewith but not shown in Fig:' 1. By the switches testing the trunk and passing it as busy. In the progress of the motion of the 1.202 because of, the shunt placed upon that winding by the connection of ground 203.

206, tn'ough meter Winding 207, contacts engagement with spring contact (I, thcrebv contacts (Z and c and conductor 203.

64 cont-a681, wiper 71-, contact of relay e1, conductor 89, ack 58, plug 51, conductor By energization oi'relav 114 path is furmshed for current from battery 30 through contacts of relay 114, conductor 25, resisting'202 to ground, energizing the core of service meter 200 and actuat ng its armatures and the counting train connected actuation of thearmatures of service meter wiper 15 and resistance 115, so that these parts now have no potential tending to produce current flowing to earth in any meters of an lines which me he brought into electric'a connection with an accessible multiple contacts by reason "or other automatic armatures of service meter 200, and prior to 203', contact ismade between parts 204 and 205, giving path for current from grounded tact 20 t, armature 205, conductor 208, conground tit-battery 9,, thus continuing the energlzationofthe core of meter 200 after current has ceased to flow through winding ,Exp'laine'd 'in connection with Fig. 3, the operation of the meter is as follows :The current to the meter by conductor 201 passes through winding 202 to ground, as above expawl e, ratchet i, and counting train K, the pawl e being always maintained in roper pm f. I Retaining pawl h holds the ratchet 'i tions; In t emovement of the armature 205,, a lpromotion n thereon of insulating 1s first drawn away from a spring closin the circuit from grounded battery 5 and a, conductor 208, etc, heretofore exilained in connection with Fig. 1. In the i'urther movement of the armature 205, the projection an presses spring contact 0 into connecting conductor 201 to ground through For the purpose of supervision and disconnection, the lamp 108 glows when the receiver at substatlon 8 is hung upon the disconnect signal by the operator at since to disconnect upon this signal would at and 92. busy test conditions are 1('!11u\'0(l from the times lead her to disconnect a trunk upon spondcd to the ring: therefore the operatorat 55 must disconnect only upon signal of lamp 93.

When the patron at substation telephone 8 hangs his tclcphouc upon the hook and opcns the circuit through that substation telephone, he interru its the current flowing through relays 41 and 10. The interruption of current flowing through relay 16 releases its armature, closing itsiarrnaturc contact and giving path for current from battery 0, through armature contact of relay 16, winding of magnet 4, contacts 45 and 46 back to battery 9, thus by the energization of n'iagnct 4 releasing the rotary part of the automatic switch 20 and permitting its return to normal; upon the return to normal of the rotary part 0 automatic switch 20, the projection 47 engages the contact spring 46 and presses it away from contact-45, opening the circuit inst described and releasing magnet 4; also by'the opening of the contact between parts 45 and 46, the circuit from grounded battery 206 through 207, 20 i, 205, 208, has been opened, and the meter 200 therefore is released also. The disengagement of wiper 13 from its waiting contact'releases relay 40, and all parts associated withthe line 17 return to their normal position of rest.

By the interruption of current therethrough, as above stated, relay 41 releases its armatures; release of armature 42 interrupts current through relay 29, which releases its armature-s; release otarmature 50 gives path for current frombattery 30, through signal lamp 4S, armature 49 of en ergized relay 9S and armature 50 of released relay 41 back to battery 30; the glowing of this lampv acts as a positive signal for dis connection for operator at 54, who then removes the plug 51 from the jack 58, releasing all relays associated with that plug. ln connection with jack 58, by the removal of plug 51 current ceases to llow through relay 59 and this relay-releases its armature and so closes its armature contacts. Thus a path is given for current from battery 76 through armature contacts of relay 59, winding of release magnet 116, contact pair 1 17.1 18 back to battery 76, thus releasing the rotary part of the automatic switch 63; by the return of switch 03 to normal, with the incident opening of contact pair 117-i18 and disconnection of the wipers 71, 72, 75), 74, 75 all relays and magncts in connection with automatic switch 63 are released and thc source oi current is disconnected from relays es. 6h, 67 By the rclcasc oi relays (30, (i8, 07,

trunk, and by thc rclcasc oi rclay 02 path is given for current from grounded battery 05', through signal lamp 03, contacts of energiZccl relay 94', contacts oi released relay 92' and to ground, causing lamp 93 to glow as? disconnect signal to the operator at 57, who i then remoyes the plug 76 from jack 96, which releases all relays, including the relay it)? oi the line 17.

it condition encountered in the testing a tion of the automatic switches requires mention. as it etlects the limitations ol design oi the apparatus required. .\ssulne in l i 1 that the trunk connected with waiting contacts oi conductors 21, 22, 23124, is busy, and that the automatic switch 20 attempts tov connect with that trunk. The waiting contact of conductor 23 is connected to the conductor 38, and relay of the line holding the trunk busy, and thence to ground; when the automatic switch it? steps its wipers into connection with the waiting contacts of this trunk, conductor 23. through its waiting contact in switch 20 is connected al o to conductor 33, and through relay 4() of the testing line, and to ground. Thus a'circuit exists trom battery 30, through armature 36, contact point 37, resistance 199, and conductor 23, thence dividing, one part passing oyer conductor 38 and winding of relay All of the line holding the trunk busy, and the other part passing over conductor 38 and winding of relay 40 ot' the line testing the trunk. with this condition existing the relay to of the line holding the trunk busy, which relay was energized and attracted its armatures at the time the trunk was taken by the line. and has held its armatures continuously since then, must not new release its armaturcs: relay 40 of the line testing thetrunk for busy must not attract its armatures. By making resistance 199 comparatively high with respect to the. resistance of the relay 40, all relays 4) being of equal resistance, the desired result is attained.

Before the trunk was tested and while it was being held busy by the first mentioned line, a circuit. existed including battery 30, armature 36, point 37, resistance 199, cond uctor 23, its waiting contact. wiper 13 of the first line, conductor 38 of the first line, conductor 32') ot the first line, and winding of relay 40 ot the first. line, over which. circuit current was flowing. By the shunting of relay 4() of the second or testing line, around the winding ol relay 40 of the first line, the total resistance of the circuit above described in detail was reduced by' one-half the amount of the resistance of one ot'the relays 40; this caused an increase of the total current flowing in the circuit, the ratio of increase being controlled by the ratio which the resistance of the relay 40 bears to the total resistance of the circuit, or to the resistance 199. It now, the resistance of the. relay 40 be small as compared with the resistance 199, the increase in current produced by the shunting of the two relays, will be small By the shunting of the two equal relays, the relays divide equally ,between themselves the total current flowing through resistance 19%), and as that current is but slightly increased over what it was betore the second relay was shunted around the first, the current received by such relay is but little more than onehalf the current which would be received by the relay 41) ot the test-- ing line. it the tested trunk were. not busy,

and which was received by the relay 4() of the first line before the second line. tested the trunk for busy. The relays 40 may be adjusted not to respond to the energization produced by that proportion of normal current received when testing a busy line; by reason of the armature being much nearer to the core of the relay after the attraction of the armature, the armature will be retained by that. degree of energization .which was insufficient to attract it in the first place. With the resistance of the relay 40 equal to onefourth of the resistance W9, and assuming the conductors external to those elements to be of negligible resistance, the current re ceived by each relay when the two are shunted together, solves to be about ot the currentreccived by one relay when the other is not shunted around it. The margin of operation of the relay -l() oi" the testing line therefore is-liberal. \Yith reference to the reduction of current to 55%ot normal for the retention of the arinatures ol the relay 40 of the tested line, it is found that relays as commonly constructed in present telephone practice require a much greater reduction thanthis Speciall constructed. relays, therefore, are not required for this circuit, the limitation being that proper relation be established between the resistance of the winding of the relay 40 and the resistance of 199 to avoid the necessity of close adjustment of relay 40.

in Fig. 1 a relation of. relays ol testing and tested circuits is encountered. similar to the one just described as to Fig. l. The relay here involved is numbered til and the series resistance involved is made up ol' the windings 87 and 88 ot the relay numbered titi. in this portion ol' the, circuit it is required that the resistance of the winding not more than one-quarter of the resistance of the windings 87 and 88, or of those windings plus an external resistance in series with them; in neglect of this relation oi resistance, some special adjustment of relay (3]. might be required.

The equipment shown in drawings Figs. l and? may be replaced with other types of equipment. Many ditl'erent devices and ar 'rangements of parts might be designed to accomplish the same results: for instance, it would bepossible obviously, to cnd'the outgoing ends of the trunk lines in plugs rather than in acks so that the operator would make a connection between a. calling ol' relay (il be i cir-' "cuit leading from the calling subscriber in a ack instead ot a plug, and to termmatc the line, is a form of manually operated switch, 'and obviousl other forms of manually op- ;erated swit'clie jacks and plugs might be-tiscd by the operas than those consisting of tors to perform their respective functions. Therefore, while I consider that my inventionis well illustrated in the drawings herewith, it is to be understood that my invention is not restricted to the specific type of apparatus shown.

What I claim as new, and desire to protect by United States Letters Patent, is:

1. In a telephone system, two central stations; a trunk extending between said central stations; multiple contacts connected With said trunk at the said central stations respectively; relays 'also at both central stations; extensions at said. central stations connecting the respective ends of said trunk with switching and signaling devices; and circuits, by which, when connection is made with said trunk at one of itsmultiple contacts at one central station, said relays at such station operate to disconnect the extension thereat from said trunk, and said rela s atthe other station 0 erate to establis busy test conditions at t iie multiple contacts of said trunk at said other station, substantially as described.

2. In a telephone system, two central'slations a trunk extending between said central stations; automatic selective switches in each of said central stations; multiple contacts in said automatic selective switches of both central stations, said contacts being connected with said trunk; relays at both central stations; extensions at said central stations connecting the respective ends of said trunk with switching and signaling devices; and circuits, by which, when connection is made with said trunk at one of its multiple contacts at one central station,said relays at each station operate to disconnect the extensionthereat' from said trunk, and

said rolaysiat the other station operate to establish b'usy test conditions at the multiple contacts of said trunk at said other station, substantiall asdescribed.

3. In a telb a relay in connection with said switching plug; a meter; circuits by which said meter is electrically operated consequent upon the encrgization of said relay; a trunk jack; an automatic switch connected with said jack; a distant switchboard; trunks terminating in said automatic switch and in said distant switchboard; mechanisms and circuits by which said automatic switch may select an idle one of said trunks and connect it to said "jack, the selected trunk including a conductor continuous for direct current and conphone system, a switching plug;

necting said switch wit h said distant switchboard; circuits by which when said switching plug is connec' ed with said jack and said jack is connected with said trunk said conductor will be connected with said relay; a source of electric potential at said distant switchboard notnormally connected with said conductor; a telephone line terminal ing in said distant switchboard; a substation telephone on said telephone line; the circuit through said telephone line and substation tcle )hone; switching devices for connecting saic' trunk to said telephone line; a relay associated with said distant switchboard and with said trunk; circuits by which said second relay is energized when said trunk is connected with said telephone line and said circuit through said telephone and substation telephone is closed; and circuits which by the energization of said second relay place the said source of electric potential in connection with the said conductor and said first relay is energized, substantially as described.

4. In a telephone system, a telephone line; a meter associated with said line; an auto matic selective switch; a manually operated switch whereby saidtelephone line may be connected with said automatic switch; a distant switchboard; a trunk terminating in said automatic switch and in said distant switchboard; automatic devices by which said switch connects said line with said trunk when said line is connected manually with said switch; a conductor included in said trunk continuous for direct current and connecting said switch with said distant switchboard; circuits by which said meter is electrically o ierated; a source of continuous and direct e ectric potential at said distant switchboard not normally impressed upon said conductor; a tele hone lino terminating in said distant switch card and including a connecting the said trunk to said latter telephone line; a relay associated with said distant switchboard and with said trunk; circuits by which said relay is encr 'izcd when lsaid trunk is connected with said telephone line and the circuit through said tele )hone line and substation telephone is closed; circuits which by the energization of said relay im ress said potential upon said conductor; an( circuits and devices associated with said automatic switch, manually operated switch andtcle'p'hone line and meter, by which said meter is actuated consequent u ion i1npressment of said potential on said conductor, substantiall as described.

5. In a te ephono system, the combination of a telephone line; an electrically operated meter; an automatic selective switch; a dis tant switchboard; a trunk terminating in said automatic switch and in said distant l switchboard; a telephone line terminating with in said distsni switchboard; a substation united conse hent upon the energization of Eeiephone 011 said iiLCtQl' telephone lirie'; manually eeersied means fer connecting said first telephone iine with said automatic switch; means for connecting said trunk said second. ili-)h0li6 line; a relay; means in "hereby seid relay is energized consequent upon the answering of said substation *seienhone upen said second telephone 10 line; and means whereby said meter is aci i i said relay. sn 'stantielly as described.

Signed by me at Bittsbu 'g, county of Allegheny, Sta teof Pennsylvania, in the presence of two witnesses.

SIDNEY HAND BROVVNE.

Witnesses ALICE M. GODFREY, Al H. MORAWEEK; 

